1. Field of the Invention
The present invention relates to a device for cleaning melt filters which are intended for filtering melts, particularly plastic material melts in extruders, and which include at least one moveable sieve disc with one or more exchangeable sieve inserts, wherein at least one sieve insert is moveable into a flow of cleaning medium within the device in such a way that the sieve insert is located above or below an inlet opening of a cleaning duct.
2. Description of the Related Art
Melt filters have the purpose of mechanically removing impurities from plastic material melts which are used, for example, in extruders. For this purpose, a melt filter includes a metal sieve disc which is provided with several sieve inserts which are arranged one after the other along the circumference.
The sieve inserts can be held at intermediate frames which may be of metal and the sieve inserts may be spaced apart from each other by means of these intermediate frames. Consequently, the intermediate frames simultaneously form separating webs. The sieve inserts themselves can also be made of metal and they can be provided with passage ducts which extend perpendicularly of the plane of extension of the sieve disc, wherein the passage ducts perform a filtering function because of their small diameters.
After a certain time of operation, it is desirable to subject the sieve insert to a cleaning process in order to remove mechanical impurities which would clog the hole ducts. Without this cleaning process, the clogged sieve areas would quickly cause a substantial counter pressure to be built up which would impair the operation of the sieves.
For carrying out the cleaning process, the sieve inserts are subjected to a flow of cleaning medium which is oppositely directed to the direction of the melt flow through the sieve discs. Accordingly, if the melt flow travels through the sieves from top to bottom, the cleaning flow will travel through the sieves from the bottom toward the top, as long as the orientation of the sieves remains the same during the cleaning process.
It is desirable to carry out the cleaning process of the sieve discs with the same effectiveness and speed as the filtering process of the melt, so that both operations can be adapted to each other and carried out simultaneously.